I. Field of the Invention
The present invention relates generally to fluid valve assemblies and, more particularly, to a fluid valve assembly of the type used in fuel pumps for internal combustion engines.
II. Description of Material Art
Modern day internal combustion engines of the type used in automotive vehicles typically use fuel injectors in order to inject the fuel into the fuel combustion chamber. Many modern day internal combustion engines, furthermore, are direct injection engines in which the fuel injectors are open directly to the internal combustion chamber.
During the operation of the engine, in order to overcome the high pressures present within the internal combustion chamber of the direct injection engine, the fuel must be delivered to the fuel injectors at a high fuel pressure. Conventionally, a high pressure fuel pump provides fuel to a fuel rail which extends along the fuel injectors. Each fuel injector is then fluidly connected to the interior fuel chamber of the fuel rail by an injector fuel port and fuel cup.
In order to achieve the high pressures necessary for the fuel injection of a direct injection engine, many previously known fuel pumps utilize a reciprocating piston within a fuel chamber in a fuel pump housing. This piston both inducts fuel from a fuel source or fuel tank during the induction stroke, and also pumps fuel from the fuel chamber out through an outlet check valve and to the fuel rail. Typically, these pistons utilize a cam lobe which is rotatably driven in synchronism with the engine so that the outer cam surface mechanically displaces the pump piston and reciprocally drives the pump piston in the pump chamber.
While these previously known direct injection internal combustion engines enjoy high efficiency, fuel economy, and other advantages, one disadvantage of such engines is that the fuel pressure pulsations within the fuel delivery system create both vibration and noise from the engine. This noise is particularly audible at low engine speeds, such as idle.
A major source of noise within the previously known fuel delivery systems arises from the operation of the outlet check valve for the fuel pump for the engine. The outlet check valve typically comprises a metallic valve which is urged towards a closed position and against a valve seat by a compression spring. During the pump or pressure cycle of the fuel pump, the pressure within the pump chamber forces the outlet valve open against the force of the spring and allows fuel to flow past the valve and to the fuel rails for the fuel injectors. Conversely, during the suction stroke of the pump pistons, the force of the compression spring urges the outlet valve against the valve seat due to the reduced pressure within the pump chamber. This cycle is then continuously repeated during the operation of the engine.
The outlet check valve from the fuel pump, however, forms a major source of noise in the fuel delivery system. This noise is due primarily to two different components.
First, the outlet check valve as well as the valve seat are typically constructed of metal for durability. Consequently, the repeated impact of the valve against the valve seat during each full cycle of the fuel pump piston creates a clicking sound which can often be heard at low engine speeds.
A second source of noise in the fuel delivery system attributable to the opening and closure of the outlet check valve from the fuel pump arises from fuel cavitation as the check valve is moved from its closed and to its open position. In particular, the fuel pump housing which forms the fuel outlet port from the fuel pump is typically constructed with a sharp edge. Consequently, once the valve is moved to its open position, the rapid flow of the fuel past the sharp edge of the port creates cavitation in the fuel which, in turn, creates noise.
A still further source of noise in the fuel delivery system arises from pressure pulsations within the fuel delivery system.